The present invention generally pertains to mixing the contents of a two-dimensional array of vessels and is particularly directed to mixing such contents by causing magnetic stir elements within the vessels to tumble in response to the rotation of magnetic flux lines.
In a prior art magnetic tumble stirring apparatus, which is described in U.S. Pat. No. 6,176,609 to Cleveland and Markle, a two-dimensional array of vessels which contain magnetic stir elements is disposed above a rotatable permanent magnet that is disposed to have its physical axis of rotation in a horizontal plane and a magnetic-flux axis in a vertical plane. Rotation of the permanent magnet causes the magnetic flux lines emanating from the magnet to rotate through 360 degrees in the vertical plane within the vessels to thereby cause the magnetic stir elements in the vessels to tumble and thereby mix the contents of the vessels.
In prior art systems in which the contents of a two-dimensional array of vessels are mixed by a vortex created by continuous lateral tumbling of a magnetic stir element within each vessel, a magnetic drive that provides magnetic flux lines of varying orientation to thereby cause the tumbling of the stir elements is positioned beneath each vessel. These systems are impractical for stirring the contents of a large array of vessels that are embodied as wells in a microplate.